1. Field of the Invention
This invention relates to improved methods and compositions for controlling foam in non-aqueous fluid systems. More particularly this invention relates to improved methods and compositions for controlling foam in synthetic phosphate ester functional fluids, particularly under conditions of use found in gas turbine lubricating systems.
2. Description of the Prior Art
Many industrial systems are particularly susceptible to foaming problems even under mild conditions of agitation. These problems can be substantial in that they do not allow full utilization of the particular equipment or process involved. In order to counteract foaming problems it is often necessary to resort to chemical treatment for the control of foam. In such chemical treatment, it is highly desirable to reduce existing foam to a low level in a short period of time, i.e. defoam, and to inhibit the foam formation over an extended period of time. Many chemical treatments are, however limited in that only one of the aforementioned effects predominate.
Most functional fluid systems, such as cooling, lubricating hydraulic fluid and heat transfer systems, have a tendency to foam, thus necessitating the addition of foam control compositions to such systems. Gas turbine lubricating systems, for example, present a difficult problem in foam inhibition in that the lubricating fluid is usually continuously filtered. Typically foam control compositions for gas turbine lubricating systems are filtered out fairly rapidly, thus limiting their foam inhibiting properties.
Generally, synthetic phosphate esters are used in functional fluid systems, particularly triaryl phosphates. Triaryl phosphates and their use as functional fluids are described in:
U.s. pat. No. 2,071,023 to Bass PA0 U.s. pat. No. 2,938,871 to Matuzzak; PA0 U.s. pat. No. 3,012,057 to Fierce et al; PA0 U.s. pat. No. 3,071,549 to Stark; PA0 U.s. pat. No. 3,468,802 to Nail; PA0 U.s. pat. No. 3,576,923 to Randall et al; PA0 U.s. pat. No. 3,723,315 to Sullivan; PA0 U.s. pat. No. 3,780,145 to Malec; PA0 U.s. pat. No. 3,931,023 to Dounchis; and PA0 U.s. pat. No. 3,992,309 to Dounchis.
The entire disclosures of all of the aforementioned patents are incorporated herein by reference.
Organo-silicone antifoam agents, and their use in controlling foam in non-aqueous fluids, such as functional fluids, is described in U.S. Pat. No. 2,357,007 to Larsen. In particular, it is known to use such organo-silicone antifoam agents for controlling foam in synthetic phosphate ester functional fluids, such as triarylphosphates, particularly in gas turbine lubricating systems. (U.S. Pat. Nos. 3,931,023 and 3,992,309). Such organo-silicone antifoam agents however tend to filter out of the system and thus do not provide long term inhibition of foaming.
Fatty acid monoalkanolamides and fatty acid dialkanolamides are known foam stabilizing agents in aqueous detergent compositions. Such stabilizing agents are used to improve the persistence and stability of foam produced in aqueous wash liquours. It is also known that these stabilizing agents, when used in combination with certain amine oxides, produce detergent compositions for aqueous systems which not only have foam stability but also reduced foaming capacity. (U.S. Pat. No. 3,470,102 to Heinze.)
It is an object of this invention to provide an improved foam control composition for controlling foam in non-aqueous fluid compositions.
It is another object of this invention to provide an improved non-aqueous fluid composition having decreased foaming tendencies.
It is still another object of this invention to provide a method of inhibiting the foaming tendencies of non-aqueous fluids.
Further objects will be apparent from the following description of the invention.